The proposed project will optimize the fabrication of an ankle foot orthosis (AFO) to address the needs of drop-foot patients. These patients are unable to dorsiflex their foot because of impaired muscle activity around the ankle. The project team has developed a prototype orthosis using a shape memory alloy (SMA) wire actuator. The actuator captures and releases energy during walking to provide dorsiflexion motion, which drop-foot patients' lack. The proposed research includes performing methodical study toward achieving super-elastic behavior in shape memory parts created using selective laser melting and developing a proof of concept shape memory hinge to capture and release energy to the ankle without the need to external sources of energy.
If successful, the proposed research could have a significant impact on the advancement of active ankle foot orthosis. Every year a large number of individuals experience a loss of ability to dorsiflex the ankle due to disease or traumatic injury to the lower extremity that resulted from automobile accident or work-related causes. Of particular note, these last two conditions associated with foot drop (traumatic brain injury and traumatic lower extremity injury) are very common among soldiers.
Project Summary: The team seeks to assess the potential for commercialization of an orthotic device that has been developed during the NSF CBET-0731087 award "Shape memory alloys actuated ankle foot orthosis." The proposed project will optimize the fabrication of an ankle foot orthosis (AFO) to address the needs of drop-foot patients. These patients are unable to dorsiflex their foot because of impaired muscle activity around the ankle. This significantly affects the patientâ€™s gait due to the foot slapping at heel strike and dragging the toe during the swing, which results in an impairment of the patientâ€™s mobility. The major causes of foot drop are trauma to the involved nerves, stroke, cerebral palsy and multiple sclerosis. The range of individuals who could potentially benefit from the proposed improved AFO is very broad. Worldwide, it has been estimated that there are more than 80 million people living with a disability that is the result of a stroke with an annual increase of 3 million. Many of these individuals experience impairment in their ability to walk. Also, many of those suffering from traumatic brain injury experience foot drop. It has been estimated that, to date, more than 25,000 US soldiers have been wounded as a result of conflicts in the Middle East. Many of these individuals will need extensive treatment and rehabilitation, and in many cases this will necessitate the use of an AFO to facilitate ambulation. As this population tends to be young and otherwise healthy, it is important that assistive devices allows for maximum mobility. The project team has developed and tested a prototype orthosis using a shape memory alloy (SMA) wire actuator. The actuator captures and releases energy during walking cycle to provide dorsiflexion motion, which is lacking in drop-foot patients. This is significant improvement over conventional AFOs, which fix the ankle and therefore limit patientsâ€™ mobility. Motion analysis testing showed improved walking gait in patients with the new AFO. If funded, the team will move the device from the prototype stage toward commercialization by developing miniaturized SMA hinges to form an aesthetically pleasing and practical AFO. To this end, rigorous research will be conducted toward optimizing manufacturing parameters to fabricate SMA hinges through selective laser melting. Keywords: orthosis, shape memory alloy, drop-foot, selective laser melting/sintering, rapid prototyping, additive manufacturing Outcomes: At the end of the I-Corps workshop the team decided not to form a business to commercialize the AFO. Based on the customer interviews however we identified the most important needs of the patients. The main needs are functionality, low profile, lightweight, and stability. To address these needs we continued the research, which has resulted in a new AFO. This AFO is light-weigh and simple while restoring the stiffness profile of the ankle using superelastic properties. The main element of the AFO is an additively manufactured innovative hinge. Initial analyses have been promising.